This research utilizes the Averaged Evoked Potential (AEP) technique to study human and animal brain function with the following objectives: to identify the neural structures whose activity is reflected in the human AEP and the neural pathways which participate in the activation of these structures; to analyze psychological phenomena which covary with alterations in the various components of the AEP; and to apply the knowledge of AEPs thus gained to clinical medicine, primarily neurology, for diagnosis and prognosis, especially prognosis for recovery of brain function, in various types of sensory neuropathology. During the period of this report we have completed or progressed on the following experiments: Topography of the averaged movement potential; Origin of early auditory evoked potentials in man: Effects of barbiturate anesthesia; Specific and nonspecific late components of the human SER; SERs recorded from the pial surface of the human brain; Studies in experimental epilepsy: 2. Effects of monomethylhydrazine (MMH) and other convulsant agents on somatic evoked potentials in the cat; Modification of EEG through biofeedback techniques; Evoked potentials in patients with epilepsy; Levels of processing in speech perception: Neurophysiological and information-processing analysis; AERs associated with temporal order judgments of dichotically presented sounds during linguistic and nonlinguistic processing; The relation between long-latency AERs and perceptual discrimination; An improved objective method for detection of absolute auditory threshold in evoked response audiometry; studies of comparative and evolutionary aspects of sleep; and sleep in the armadillo, Dasypus novemcinctus.